Concentrated aqueous dye compositions containing a low molecular weight amide and their use for dyeing paper

ABSTRACT

Concentrated, liquid preparations of metal-free direct azo dyes which contain in each instance 1 part by weight of dye, 1 to 8 parts by weight of water, and 0.5 to 5 or preferably 0.5 to 2 parts by weight of an amide are useful for dyeing paper in the stock and for dyeing paper sheet.

This application is a division of application Ser. No. 739,213, filed on June 24, 1968 and now abandoned.

DESCRIPTION

This invention relates to concentrated, liquid preparations of metal-free direct dyes of the azo series, which contain in each instance 1 part by weight of dye, 1 to 8 parts by weight of water, and 0.5 to 5 or preferably 0.5 to 2 parts by weight of an acid amide. Mixtures of acid amides may be employed if desired. All water-soluble metal-free direct dyes, in particular those of the disazo and trisazo series, or mixtures of such dyes are suitable for the production of these preparations.

Highly suitable dyes for this purpose are substantive disazo dyes of the formula

    F.sub.1 -- A -- F.sub.2                                    (I)

where F₁ and F₂ represent radicals of identical or different monazo dyes bearing water-solubilizing groups and A represents a bridge member, for example an imino group or the radical of a diamide of carbonic, fumaric or cyanuric acid.

Dyes of similarly good suitability are substantive disazo dyes of the formula

    K.sub.1 -- N = N -- B -- N = N -- K.sub.2                  (II),

where B represents the radical of a tetrazo component of the diphenyl series and K₁ and K₂ represent identical or different coupling components bearing water-solubilizing groups.

Suitable water-solubilizing groups are carboxylic and sulphonic acid amide groups and preferably the sulphonic acid group.

The substantive azo dyes contain preferably 1 to 4 water-solubilizing groups per azo group.

The amides of inorganic or organic acids may be employed as acid amides, but carboxylic acid amides are preferred, e.g. those of monobasic or dibasic carboxylic acids such as the amides of carboxylic acids of low molecular weight containing, e.g. 2 to 4 carbon atoms, e.g. acetamide, propionic acid amide, butyric acid amide and malonic acid diamide. Urea and urea derivatives are particularly well suited; examples, besides urea itself, are substituted or unsubstituted alkylurea compounds such as methyl and ethyl urea, N,N'-dimethyl urea, dihydroxyalkyl urea, etc. Further, guanidine and its derivatives such as methyl guanidine are well suited, and so are the formamides, e.g. formamide itself and alkylformamides such as methyl and dimethylformamide. Sulphonic acid amides, e.g. sulphonic acid diamides, are also suitable for the production of the dye preparations of this invention.

The dye preparations are produced by mixing the aforenamed components and heating the mixture for a short time if necessary. The preparations may contain further assistants if desired, for instance dyeing assistants if used for textile dyeing or paper auxiliary products if used for paper dyeing, such as pH-stabilizing agents, e.g. amino acids, phosphates and acetates. The urea component itself can be employed as a pH-stabilizing agent. Other additions which the preparations may contain are softeners, water repellent agents, dispersing agents and agents for improving the wet tensile strength.

In French Patent 1,420,403 dyeing preparations are described which contain 1 part by weight of dye, 0.01 to 75 parts by weight of water and 2 to 100 parts by weight of an acid amide. These preparations are employed solely for the dyeing of leather and accordingly they contain only leather dyes, in particular metal complex dyes. In all the examples of the named French patent metal complex dyes are employed. No mention is made of metal-free direct dyes.

The advantage of the new preparations is that they contain substantially smaller amounts of acid amide. Hence, they are more economical and the waste water from dyeing is less heavily contaminated.

The new preparations can be employed for the dyeing of paper, either as true aqueous solutions or as dispersions diluted with water as necessary. They are equally suitable for dyeing paper in the stock and by dipping and coating techniques.

Another advantage of the dyeing preparations here disclosed is that they are easier to handle. There is no inconvenient dusting in weighing out as with powder dyes and the liquid form makes them well suited for application in continuous dyeing processes.

The preparations are storable for several months at room temperature. They are not affected by frost and are immune to mould growth.

In the following Examples the parts and percentages are by weight and the temperatures in degrees centigrade.

EXAMPLE 1

62.4 Parts of the sodium salt of the disazo dye of the formula ##STR1## in the form of a 50% aqueous paste are stirred in 275 parts of water to form a homogeneous mixture and dissolved by the addition of 100 parts of urea. The dye solution is then made up to 500 parts. It is storable for several months at room temperature. When employed for dyeing paper in the stock, this liquid preparation gives bright yellow dyeings.

EXAMPLE 2

68.4 Parts of the sodium salt of the disazo dye of the formula ##STR2## as a 55% aqueous paste are added to 275 parts of water at 40° and stirred to form a homogeneous mixture, whereupon the dye is brought into solution by adding 100 parts of urea. The solution is filtered to eliminate small amounts of insoluble impurities, after which 500 parts of a preparation are obtained which is storable for several months at room temperature. With this liquid preparation bright yellow paper dyeings are obtained.

EXAMPLE 3

A 40% aqueous paste of 95.6 parts of the sodium salt of the disazo dye D.I. Direct Yellow 50 (Colour Index, 2nd ed., No. 29025) having the formula ##STR3## are homogeneously mixed with 160 parts of water, with the subsequent addition of 200 parts of urea. On heating to 70°-80° the dye goes into solution. The solution is filtered with the addition of 5 parts of "Hyflo" (registered trade mark) filter earth and cooled. 600 Parts of a liquid preparation are obtained which is storable for several months at room temperature. It gives bright reddish yellow dyeings on paper.

EXAMPLE 4

101.6 Parts of the sodium salt of the disazo dye C.I. Direct Yellow 34 (Colour Index, 2nd ed., No. 29060) having the formula ##STR4## in the form of a 37% aqueous paste are homogeneously mixed with 415 parts of water, after which 175 parts of urea are added and the temperature increased to 85°-90°, at which temperature the dye goes into solution. 6 Parts of "Hyflo" filter earth are added and the solution is filtered to give 865 parts of a liquid dye preparation. The preparation is storable for several months at room temperature and gives bright golden yellow dyeings on paper.

EXAMPLE 5

126.4 Parts of the sodium salt of the disazo dye of the formula ##STR5## as a 40% aqueous paste are added with stirring to a solution of 250 parts of urea and 310 parts of water and dissolved by raising the temperature to 60°-70°. 5 Parts of "Hyflo" filter earth are added and the solution filtered to yield 875 parts of a liquid dye preparation which is storable for several months at room temperature. With this preparation bright scarlet paper dyeings can be produced.

EXAMPLE 6

99.2 Parts of the sodium salt of the disazo dye C.I. Direct Blue 15 (Colour Index, 2nd ed., No. 24400) having the formula ##STR6## in the form of a 50% aqueous paste are dissolved in a solution of 152 parts of urea and 410 parts of water at room temperature. After the addition of 4 parts of "Hyflo" filter earth the solution is filtered. 760 Parts of a dye preparation are obtained which is storable at room temperature for several months. It gives bright blue dyeings on paper.

EXAMPLE 7

99.2 Parts of the sodium salt of the disazo dye C.I. Direct Blue 1 (Colour Index, 2nd ed., No. 24410) having the formula ##STR7## as a 50% aqueous paste are homogeneously mixed with 402 parts of water and dissolved at room temperature by the addition of 200 parts of urea. The solution is clarified by filtration using 5 parts of "Hyflo" filter earth. The product is 800 parts of a dye preparation which is storable for several months at room temperature and gives bright blue paper dyeings.

Dyeing Example A

0.3 Parts of the dyeing preparation as described in Example 2 are added to a stock of 100 parts of chemically bleached sulphite cellulose in 2000 parts of water while it is being beaten in the beater. After 15 minutes the stock is sized which fixes the dyeing. Paper fabricated from this stock is dyed in a yellow shade of medium depth and the fastness properties of the dyeing are good. The back-water is colourless.

Paper dyeings of similar shade can be obtained when the dyes of Examples 2, 4 and 24a are applied as they are without further preparation by the methods described in Dyeing Examples A or B.

Dyeing Example B

A change of 70 parts of chemically bleached sulphite cellulose from coniferous wood pulp and 30 parts of chemically bleached sulphate cellulose from birchwood pulp in 2000 parts of water is mechanically treated in the pulper and at a suitable point 0.2 parts of the liquid dye preparation of Example 4 are added to it. After a further 20 minutes' processing the stock is converted into absorbent paper dyed in a golden yellow shade of medium depth.

Further liquid dye preparations of similarly good quality can be prepared in accordance with the procedures of Examples 1 to 7 with the dyes of the following Table 1, which are of the general formula

    C -- N = N -- D -- NH -- X -- HN -- E -- N = N -- F

The meanings of C, D, E, F and X are noted in the appropriate columns of the table.

                                      TABLE 1                                      __________________________________________________________________________     Example                                                                             C         D        E         F        X       Shade on                    No.  = Radical of                                                                             = Radical of                                                                            = Radical of                                                                             = Radical of                                                                            = Radical of                                                                           paper                       __________________________________________________________________________      8   1-Aminobenzene-                                                                          1-Amino-2-meth-                                                                         1-Amino-3-methyl-                                                                        2-Aminonaphtha-                                                                         Phosgene                                                                               yellow                           3-sulphonic acid                                                                         oxybenzene                                                                              benzene   lene-4,8-disul-                                                                phonic acid                                   9   2-Aminonaphtha-                                                                          1-Amino-3-meth-                                                                         as D      as C     "       "                                lene-5,7-disul-                                                                          ylbenzene                                                            phonic acid                                                               10   2-Aminonaphtha-                                                                          "        as D      as C     "       "                                lene-6,8-disul-                                                                phonic acid                                                               11   "         "        1-Amino-3-methyl-                                                                        as C     Fumaric acid                                                                           "                                                   benzene                                                12   1-Amino-2-methyl-                                                                        2-Amino-5-hydr-                                                                         as D      as C     Phosgene                                                                               orange                           benzene-4,6-di-                                                                          oxynaphthalene-                                                      sulphonic acid                                                                           7-sulphonic                                                                    acid                                                            13   1-Amino-2-meth-                                                                          "        as D      as C     "       yellowish                        ylbenzene-4-                                  scarlet                          sulphonic acid                                                            14   1-Amino-4-meth-                                                                          "        as D      as C     "       "                                ylbenzene-3-                                                                   sulphonic acid                                                            15   1-Amino-4-meth-                                                                          "        as D      as C     "       scarlet                          oxybenzene-3-                                                                  sulphonic acid                                                            16   1-Amino-4-meth-                                                                          2-Amino-5-hydro-                                                                        as D      as C     Phosgene                                                                               scarlet                          oxybenzene-2-                                                                            oxynaphthalene-                                                      sulphonic acid                                                                           7-sulphonic acid                                                17   1-Amino-2-meth-                                                                          "        as D      as C     "       "                                oxybenzene-4-                                                                  sulphonic acid                                                            18   2-Aminonaphtha-                                                                          "        as D      as C     "       "                                lene-4,8-disul-                                                                phonic acid                                                               19   2-Aminonaphtha-                                                                          "        as D      as C     "       "                                lene-6,8-disul-                                                                phonic acid                                                               20   2-Aminonaphtha-                                                                          "        as D      2-Aminonaph-                                                                            "       "                                lene-4,8-disul-              thalene-6-sul-                                    phonic acid                  phonic acid                                  21   3-Acetylamino-                                                                           "        as D      as C     "       "                                1-aminobenzene-                                                                6-sulphonic acid                                                          22   2-Aminonaphtha-                                                                          "        as D      as C     2-Amino-4,6-                                                                           "                                lene-4,8-disul-                       dichloro-1,3,5-                          phonic acid                           triazine                            23   "         "        as D      as C     2-Phenylamino-                                                                         "                                                                      4,6-dichloro-                                                                  1,3,5-triazine                      24   2-Aminophtha-                                                                            "        as D      as C     2-Phenylamino-                                                                         "                                lene 5,7-disul-                       4,6-dichloro-                            phonic acid                           1,3,5-triazine-                                                                3'-sulphonic                                                                   acid                                 24a 2-Aminonaphtha-                                                                          2-Amino-5-hydr-                                                                         as D      as C     Phosgene                                                                               scarlet                          lene-6-sulpho-                                                                           oxynaphthalene-                                                      nic acid  7-sulphonic acid                                                25   1-Aminonaphtha-                                                                          "        as D      as C     "       red                              lene-4,6-disul-                                                                phonic acid                                                               26   1-Aminonaphtha-                                                                          "        as D      as C     "       "                                lene-5-sulpho-                                                                 nic acid                                                                  __________________________________________________________________________      Similarly good dye preparations can be prepared in accordance with             Examples 1 to 7 using the dyes set out in the following Table 2, which ar      of formula (II) and in which the symbols K.sub.1, K.sub.2 and B have the       meanings assigned to them in the appropriate columns.                    

                                      TABLE 2                                      __________________________________________________________________________     Example                                                                             K.sub.1     K.sub.2   B                                                   No.  = Radical of                                                                               = Radical of                                                                             = Radical of                                                                               Shade on paper                          __________________________________________________________________________     27   1-Amino-8-hydroxy-                                                                         1-Amino-8-hydroxy-                                                                       4,4'-Diamino-1,1'-                                                                         reddish blue                                 naphthalene-3,6-di-                                                                        naphthalene-3,6-di-                                                                      diphenyl                                                 sulphonic acid                                                                             sulphonic acid                                                28   "           "         4,4'-Diamino-3,3'-                                                                         blue                                                               dimethyl-1,1'-diphenyl                              29   1,8-Dihydroxynaphtha-                                                                      "         4,4'-Diamino-3,3'-                                                                         "                                            lene-3,6-disulphonic  dimethoxy-1,1'-diphenyl                                  acid                                                                      30   "           1,8-Dihydroxynaph-                                                                       "           "                                                        thalene-3,6-disul-                                                             phonic acid                                                   31   "           "         4,4'-Diamino-3,3'-                                                                         "                                                                  dimethyl-1,1'-diphenyl                              32   1-Amino-8-hydroxynaph-                                                                     as K.sub.1                                                                               4,4'-Diamino-3,3'-di-                                                                      "                                            thalene-2,4-disulphonic                                                                              methoxy-1,1'-diphenyl                                    acid                                                                      __________________________________________________________________________      Similarly good liquid dye preparations can be prepared in accordance with      Examples 1 to 7 with the dyes enumerated in the following Table 3.       

                                      TABLE 3                                      __________________________________________________________________________     Example                                    Shade on                            No           Dye Constitution              paper                               __________________________________________________________________________      33                                                                                  ##STR8##                              greenish  yellow                    34                                                                                  ##STR9##                              reddish yellow                      35                                                                                  ##STR10##                             scarlet                             36                                                                                  ##STR11##                             red                                 37                                                                                  ##STR12##                             red                                 39                                                                                  ##STR13##                             red                                 40                                                                                  ##STR14##                             red                                 41                                                                                  ##STR15##                             bluish red                          42                                                                                  ##STR16##                             blue red                            43                                                                                  ##STR17##                             black                               44                                                                                  ##STR18##                             black                              __________________________________________________________________________

The composition of further liquid dye preparations conforming to the invention is set forth in Table 4 below. The tabulation gives the number of parts by weight of dye in the preparation and the number of the Example in Table 1, 2 or 3 which identifies the dye, the number of parts of acid amide or acid amide mixture, and the number of parts of water.

                  TABLE 4                                                          ______________________________________                                         Example                                  Parts                                 No.    Parts  Dye of Example                                                                              Parts                                                                               Acid amide                                                                              Water                                 ______________________________________                                         45     1.0    No. 2        0.5  Urea     8.0                                   46     1.0    No. 4        0.5  "        8.0                                   47     1.0    No. 6        0.5  "        8.0                                   48     1.0    No. 1        5.0  "        6.0                                   49     1.0    No. 2        5.0  "        6.0                                   50     1.0    No. 9        5.0  "        6.0                                   51     1.0    No. 2        2.5  "        3.5                                   52     1.0    No. 4        1.0  "        6.0                                   53     1.0    No. 11       3.0  "        6.0                                   54     1.0    No. 24a      2.0  "        7.0                                   55     1.0    No. 42       2.0  "        4.0                                   56     1.0    No. 43       4.0  "        6.0                                   57     1.0    No. 16       5.0  "        8.0                                   58     1.0    No. 24       5.0  "        8.0                                   59     1.0    No. 8        5.0  "        8.0                                   60     1.0    No. 28       5.0  "        8.0                                   61     1.0    No. 37       5.0  "        8.0                                    61a   1.0    No. 2        2.0  "        6.0                                    61b   1.0    No. 4        2.0  "        6.0                                   62     1.0    No. 2        0.5  Formamide                                                                               8.0                                   63     1.0    No. 4        0.5  "        8.0                                   64     1.0    No. 5        0.5  "        8.0                                   65     1.0    No. 6        0.5  "        8.0                                   66     1.0    No. 13       0.5  "        8.0                                   67     1.0    No. 24a      0.5  "        8.0                                   68     1.0    No. 2        5.0  "        1.0                                   69     1.0    No. 4        5.0  "        1.0                                   70     1.0    No. 7        5.0  "        1.0                                   71     1.0    No. 27       5.0  "        1.0                                   72     1.0    No. 1        5.0  "        8.0                                   73     1.0    No. 3        5.0  "        8.0                                   74     1.0    No. 5        5.0  "        8.0                                   75     1.0    No. 7        5.0  "        8.0                                   76     1.0    No. 2        1.0  Formamide                                                                               4.0                                   77     1.0    No. 4        2.0  "        4.0                                   78     1.0    No. 7        2.0  "        4.0                                   79     1.0    No. 24a      3.0  "        5.0                                   80     1.0    No. 26       4.0  "        5.0                                   80a    1.0    No. 24a      2.0  "        8.0                                   81     1.0    No. 2        0.5  Acetamide                                                                               8.0                                   82     1.0    No. 6        0.5  "        8.0                                   83     1.0    No. 27       0.5  "        8.0                                   84     1.0    No. 2        5.0  "        4.0                                   85     1.0    No. 7        5.0  "        4.0                                   86     1.0    No. 4        5.0  "        8.0                                   87     1.0    No. 30       5.0  "        8.0                                   88     1.0    No. 32       3.0  "        6.0                                   89     1.0    No. 2        1.2  Urea     4.0                                                              0.8  Formamide                                      90     1.0    No. 4        1.5  Urea     7.0                                                              0.5  Ethyl urea                                     91     1.0    No. 13       3.0  Formamide                                                                               3.0                                                              1.0  Methylforma-                                                                   mide                                           92     1.0    No. 24a      2.0  Urea     8.0                                                              1.0  Formamide                                      93     1.0    No. 27       1.0  Formamide                                                                               6.0                                                              1.0  Methylforma-                                                                   mide                                           94     1.0    No. 24a      1.5  Urea     8.0                                                              0.3  Formamide                                      ______________________________________                                    

The dyes of formula (I) can be produced by the method described in German Patents 122,904, 132,511 and 216,666. Dyes of formula (I) in which A stands, for example, for the radical of a cyanuric acid can be produced in accordance with German Patent 436,179.

Dyes of formula (II) can be obtained by the process of German Patent 74,593.

The dye of Example 33 is produced in accordance with German Patent 293,333,that of Example 37 with German Patent 48,465, that of Example 42 with German Patent 114,841, and the dyes of Examples 43 and 44 in accordance with German Patent 153,559.

The dyes of Examples 33 to 37 are known from German Patent 48,465, but they can also be produced by the process of German Patent 293,333.

The dye of Example 24a can be produced by any of the known methods as follows:

(a) coupling 2 moles of diazotized 2-naphthylamine-6-sulphonic acid with 1 mole of 5,5'-dihydroxy-7,7'-disulpho-2,2'-dinaphthyl urea; (b) coupling diazotized 2-naphthylamine-6-sulphonic acid with 2-amino-5-hydroxynaphthalene-7-sulphonic acid and reacting 2 moles of the resulting compound with phosgene; (c) coupling diazotized 2-naphthylamine-6-sulphonic acid with 2-acylamino-5-hydroxynaphthalene-7-sulphonic acid, saponifying the acylamino group and reacting the resulting compound with phsogene.

Similarly good dye preparations are obtained by using lactams or lactam mixtures. For example, the urea used in Examples 1 to 7 can be replaced by lactams or mixtures of lactams; such a preparation can be prepared as follows:

EXAMPLE 95

106 Parts of the sodium salt of the disazo dye of Example 24a in the form of a 38% aqueous paste are homogeneously stirred in 665 parts of water, and after the addition of 350 parts of γ-butyrolactam the mixture is raised to 85°-90°, whereupon the dye goes into solution. 5 Parts of "Hyflo" filter earth are added and the solution filtered clear, giving 1294 parts of a liquid dye preparation which is storable for several months at room temperature. Bright red paper dyeings can be produced with this preparation.

Dye preparations of similarly good quality are obtained when the butyrolactam is replaced by ε-caprolactam.

EXAMPLE 96

100 Parts of chemically bleached sulphite cellulose in 2000 parts of water are beaten in a beater. 0.03 Parts of the dye of the formula ##STR19## are added and after 15 minutes the stock is sized, which fixes the dyeing. Paper made from this stock is dyed in a yellow shade of medium depth. Paper dyeings of similar shade can be obtained by the procedure of this Example using the dye of formula (b) or (c) in place of the one of Example 96. ##STR20## 

Having thus disclosed the invention what we claim is:
 1. In a process for producing colored paper comprising incorporating into paper stock an effective amount of a dye composition and forming paper from said paper stock said effective amount being an amount sufficient to impart the desired color to the paper, the improvement wherein the dye composition is a concentrated, liquid dye composition comprising (i) 1 part by weight of a dye or a mixture thereof, (ii) 0.5-5 parts by weight of urea and (iii) 1 to 8 parts by weight of water, wherein said dye is a dye of the formula

    R.sub.11 --N= N--R.sub.13 --A--R.sub.14 --N=N--R.sub.12 or

    K.sub.1 --N=N--B--N=N--K.sub.2,

or a salt thereof, wherein each of R₁₁ and R₁₂ is independently ##STR21## wherein R₂₁ is hydrogen, methyl or methoxy, and n is 1 or 2, ##STR22## wherein R₂₂ is hydrogen or methoxy, and R₂₃ is hydrogen or methyl, ##STR23## wherein R₂₂ is hydrogen or methoxy, and R₂₃ is hydrogen or methyl, A is --NH--, --NH--CO--NH--, trans--NH--CO-- CH=CH--CO--NH-- or ##STR24## wherein R₂₄ is hydrogen, phenyl or 3-sulfophenyl, each of K₁ and K₂ is independently ##STR25## wherein R₂₅ is --NH₂ or --OH, and ##STR26## wherein each R₂₆ is hydrogen, methyl or methoxy.
 2. A process according to claim 1 wherein said concentrated, liquid dye composition consists essentially of (i) 1 part by weight of a dye or a mixture thereof, (ii) 0.5 to 5 parts by weight of urea and (iii) 1 to 8 parts by weight of water.
 3. A process according to claim 2 wherein said dye composition comprises 0.5 to 2 parts by weight of urea.
 4. A process according to claim 2 wherein said dye is a dye of the formula

    R.sub.11 --N=N--R.sub.13 --A--R.sub.14 --N=N--R.sub.12

or a salt thereof, wherein each of R₁₁ and R₁₂ is independently ##STR27## wherein R₂₁ is hydrogen, methyl or methoxy, and n is 1 or 2, ##STR28## wherein R₂₂ is hydrogen or methoxy, and R₂₃ is hydrogen or methyl, ##STR29## wherein R₂₂ is hydrogen or methoxy, and R₂₃ is hydrogen or methyl, A is --NH--, --NH--CO--NH--, trans---NH--CO-- CH=CH--CO--NH-- or ##STR30## wherein R₂₄ is hydrogen, phenyl or 3-sulfophenyl.
 5. A process according to claim 2 wherein said dye is a dye of the formula

    K.sub.1 --N=N--B--N=N--K.sub.2,

or a salt thereof, wherein each of K₁ and K₂ is independently ##STR31## wherein R₂₅ is --NH₂ or --OH, and ##STR32## wherein each R₂₆ is hydrogen, methyl or methoxy.
 6. A process according to claim 1 wherein said dye is a dye of the formula

    R.sub.11 --N=N--R.sub.13 --A--R.sub.14 --N=N--R.sub.12

or a salt thereof, wherein each of R₁₁ and R₁₂ is independently ##STR33## wherein R₂₁ is hydrogen, methyl or methoxy, and n is 1 or 2, ##STR34## wherein R₂₂ is hydrogen or methoxy, and R₂₃ is hydrogen or methyl, ##STR35## wherein R₂₂ is hydrogen or methoxy, and R₂₃ is hydrogen or methyl, A is --NH--, --NH--CO--NH--, trans---NH--CO-- CH=CH--CO--NH-- or ##STR36## wherein R₂₄ is hydrogen, phenyl or 3-sulfophenyl.
 7. A process according to claim 6 wherein A is --NH--CO--NH--.
 8. A process according to claim 7 wherein said dye is the dye of the formula ##STR37## or a salt thereof.
 9. A process according to claim 8 wherein said direct disazo, substantive, direct disazo dye is the dye of the formula ##STR38##
 10. A process according to claim 7 wherein said dye is the dye of the formula ##STR39## or a salt thereof.
 11. A process according to claim 7 wherein said dye is the dye of the formula ##STR40## or a salt thereof.
 12. A process according to claim 7 wherein said dye is the dye of the formula ##STR41## or a salt thereof.
 13. A process according to claim 1 wherein said dye is a dye of the formula

    K.sub.1 --N=N--B--N=N--K.sub.2,

or a salt thereof, wherein each of K₁ and K₂ is independently ##STR42## wherein R₂₅ is --NH₂ or --OH, and ##STR43## wherein each R₂₆ is hydrogen, methyl or methoxy.
 14. A process according to claim 13 wherein said dye is the dye of the formula ##STR44## or a salt thereof.
 15. In a process for producing colored paper comprising treating paper sheet with an effective amount of a dye composition, said effective amount being an amount sufficient to impart the desired color to the paper, the improvement wherein said dye composition is a concentrated, liquid dye composition comprising (i) 1 part by weight of a dye or a mixture thereof, (ii) 0.5-5 parts by weight of urea and (iii) 1 to 8 parts by weight of water, wherein said dye is a dye of the formula

    R.sub.11 --N=N--R.sub.13 --A--R.sub.14 --N=N--R.sub.12

or

    K.sub.1 --N=N--B--N=N--K.sub.2,

or a salt thereof, wherein each of R₁₁ and R₁₂ is independently ##STR45## wherein R₂₁ is hydrogen, methyl or methoxy, and n is 1 or 2, ##STR46## wherein R₂₂ is hydrogen or methoxy, and R₂₃ is hydrogen or methyl, ##STR47## wherein R₂₂ is hydrogen or methoxy, and R₂₃ is hydrogen or methyl, A is --NH--, --NH--CO--NH--, trans--NH--CO-- CH=CH--CO--NH-- or ##STR48## wherein R₂₄ is hydrogen, phenyl or 3-sulfophenyl each of K₁ and K₂ is independently ##STR49## wherein R₂₅ is --NH₂ or --OH, and ##STR50## wherein each R₂₆ is hydrogen, methyl or methoxy.
 16. A process according to claim 15 wherein said concentrated, liquid dye composition consists essentially of (i) 1 part by weight of a dye or a mixture thereof, (ii) 0.5 to 5 parts by weight of urea and (iii) 1 to 8 parts by weight of water.
 17. A process according to claim 15 wherein said dye is a dye of the formula

    R.sub.11 --N=N--R.sub.13 --A--R.sub.14 --N=N--R.sub.12,

or a salt thereof, wherein each of R₁₁ and R₁₂ is independently ##STR51## wherein R₂₁ is hydrogen, methyl or methoxy, and n is 1 or 2, ##STR52## wherein R₂₂ is hydrogen or methoxy, and R₂₃ is hydrogen or methyl, ##STR53## wherein R₂₂ is hydrogen or methoxy, and R₂₃ is hydrogen or methyl, A is --NH--, --NH--CO--NH--, trans--NH--CO-- CH=CH--CO--NH-- or ##STR54## wherein R₂₄ is hydrogen, phenyl or 3-sulfophenyl.
 18. A process according to claim 15 wherein said dye is a dye of the formula

    K.sub.1 --N=N--B--N=N--K.sub.2,

or a salt thereof, wherein each of K₁ and K₂ is independently ##STR55## wherein R₂₅ is --NH₂ or --OH, and ##STR56## wherein each R₂₆ is hydrogen, methyl or methoxy. 